The present invention relates to a method for manufacturing a bent glass sheet, said method comprising
heating a glass sheet in a furnace upon rotating rollers,
bringing a glass sheet onto a bending mould located in the furnace,
bending a glass sheet in the furnace by curving the configuration of the bearing surface of the bending mould, and
carrying the bending mould out of the furnace after a bending operation and into a chilling section together with a curved glass sheet.
The invention relates also to an apparatus for manufacturing a bent glass sheet, said apparatus comprising
a furnace provided with a conveyor formed by rotating rollers and heating means for heating a glass sheet carried on the rollers close to a softening temperature, and
a mould station fitted inside the furnace and provided with a bending mould having a curveable bearing surface, said mould being transferable out of the furnace while carrying a glass sheet bent to a given curvature.
The bending of architectural glass is becoming more popular but the bending/tempering of large glasses has been problematic in an effort to achieve a sufficient capacity.
This problem has been resolved with the invention in a manner that the bending of a glass sheet is effected in a furnace upon an adjustable roller mould which is carried out of the furnace for tempering and/or chilling. The characterizing features of a method of the invention are set forth in more detail in the annexed claim 1 and the characterizing features of an apparatus are set forth in claim 10.
Prior known is the bending of a glass sheet in a furnace by using curved rollers or rolls. However, such a method has been restricted to the bending of small glasses and the bending of large building glasses (e.g. 2.times.3 mm) e.g. to an arch corresponding to a 90.degree. sector is not possible.
For example, U.S. Pat. Nos. 3,846,104 and 4,437,871 disclose the bending of a glass sheet in a furnace between shaping surfaces, the upper shaping surface serving also as a vacuum pickup. A glass sheet is carried upon the mould from the furnace to an annealing operation. Such particular mould structures are suitable for bending rather small glass sheets such as windshields but not for bending major architectural glasses to a curvature with a rather large sector angle.
U.S. Pat. No. 2,223,124 discloses the bending of a glass sheet with a roller mould by adjusting the position of rollers in vertical direction. The rollers are not associated with a displaceable roller mould but are disposed in a space for effecting therein both heating and tempering. Since a glass sheet is heated and tempered in one and the same space, the apparatus is not fit for continuous production but, instead, is very slow indeed. It is not capable of a capacity required by modern production.
Prior known is also a bending/tempering operation effected outside a furnace by using a curveable roller conveyor as a bending mould (EU 0261611). Also this method is restricted to the production of relatively small glass sheets and is not suitable for manufacturing the above-described large bent glasses. In addition, especially the bending of thin glass sheets cannot be managed with an acceptable tempering result as thin glass will be necessarily cooled before a tempering blast is started.
A method and apparatus of the invention are capable of eliminating the above limitations and drawbacks.